Downhole tool

ABSTRACT

A hydraulic lock for locking the position of an actuation member of a downhole tool relative to the body of the downhole tool is described. The hydraulic lock comprises first and second fluid chambers fluid communication between which is provided by a first fluid conduit. Located with the first fluid conduit is a first logic controlled valve that is moveable between an open configuration and a closed configuration to selectively permit fluid communication between the first and second chambers. The hydraulic lock further comprises a secondary control mechanism that provides a second means to selectively permit fluid communication between the first and second chambers. Incorporating the secondary control mechanism within the hydraulic lock provides a means for increasing the reliability and working lifetime of the hydraulic lock. It also provides a means for reducing the risk of unintentional or false activation of the hydraulic lock.

The present invention relates to downhole tools used in the oil industry. In particular to downhole tools which are activated by remote control for example by sending a pressure signal from the surface to the downhole tool.

In the oil and gas industry within downhole drilling and production completion operations there is a requirement to remotely operate downhole tools and equipment by command or action carried out at surface.

This can be achieved in numerous ways with a variety of actuation arrangements, the most common of which is the use of hydraulic pressure generated in the fluid pumped down the hole through the drilling or production tubular. For example, the pressure of a pumped fluid through a nozzle can be used to apply a force to an actuation member e.g. a piston which in turn activates a downhole tool. Typically these tools may be an expandable underreamer, expandable casing mill, side port circulating tool or similar device.

As fluid circulation is required for other purposes such as in the actual drilling operation it is important that the actuation mechanism or arrangement is selective and can differentiate between fluid flow that is required to activate the device and fluid flow that is required for the drilling operation. In this situation again there are a number of approaches that are in current use. For example, the use of a threshold pressure which is above that required for normal drilling operations acting on a spring loaded piston. In this example the tool or device will operate whenever the threshold pressure is exceeded and is sufficient to overcome the strength of the return spring. This simple approach, though effective in some applications has a number of disadvantages, namely:

-   -   there may not be a positive indication at the surface that the         activation has taken place;     -   the activation may not be a positive action but happen slowly or         partially unless shear pins are employed to ensure that the         increased pressure is applied above that required to overcome         the spring return force;     -   the activation may only be partial due to seal friction and or         other factors such as the ingress of mud solids into the moving         parts of the system; and     -   after activation the tool will de-activate due to force of the         return spring whenever and if the flow and pressure is reduced         below the threshold pressure.

An alternative actuation arrangement involves the use of a drop ball pumped down from surface onto a ball seat in the piston. This actuation arrangement will overcome some of the above disadvantages but introduces others such as:

-   -   introducing a undesirable restriction into the flow path which         could obstruct flow or the passage of other tools;     -   the drop ball will take a considerable time to reach the ball         seat, this will have a cost penalty and could have detrimental         safety implications; and     -   repeat operations may not be possible.

There are more complex actuation arrangements currently used in the industry where a number of sequential balls may be dropped to land on a deformable ball seat or releasing mechanism. These systems do allow a finite number of repeat operations but have been found unreliable in the past and tend to be quite complex.

More recently there has been the development of an actuation arrangement based on the use of Radio Frequency Identification Devices (RFID tag) to transfer instructions from surface to a downhole tool. These systems consist of introducing a small RFID tag into the flow stream and allowing it to be carried down the tubular to the downhole tool. The downhole tool recognises the RFID tag and will take a pre-programmed action. The main advantages of the RFID tag system are that it is repeatable a large number of times and does not cause a restriction in the flow path. However RFID tags still suffer the time delay disadvantages of a drop ball system in that they require time to reach the downhole tool. In some applications a drop ball actuation arrangement may even be preferable, since if flow cannot be established the ball can still fall under its own weight, whereas the RFID tag cannot.

More recently still, international patent application WO 2014/009756 teaches a system wherein a hydraulic lock positioned in the tubular string can make use of a pre-programmed surface signal, such as multiple pump operations to activate a downhole tool. The disclosed hydraulic lock comprises an actuator in the form of a logic controlled valve. The logic controlled valve acts to release the lock when it recognises a pre-programmed signal which could be pressure, rotation or linear translation for instance. After a pre-programmed time the actuator arrangement may re-imposes the hydraulic lock thereby locking the downhole tool in the activated position. In order to de-activate the tool the signal is again sent to the logic controlled valve actuator arrangement. This sequence can be repeated a large number of times.

The advantages of the above system include; real-time operation in that there is no reliance on pump down objects, no restriction in the flow path which may obstruct future operations, large number of repeatable operations and pre-programmable to look for a signal appropriate to the particular operation.

However, the hydraulic locks of the systems disclosed within international patent application WO 2014/009756 are relatively complex and so exhibit the potential for mechanical failure. Such mechanical failure is particularly problematic when the failure occurs when the downhole tool (e.g. an expandable underreamer or mill) is locked in its deployed configuration as this results it being extremely difficult to subsequently recover the downhole tool from the well.

There is also a risk that the hydraulic locks of these systems may be cause an unintentional or false activation of the downhole tool. Such accidental activation of the hydraulic lock, and thus the associated downhole tool, could have serious consequences in terms cost and safety for the operator.

SUMMARY OF INVENTION

It is therefore an object of an aspect of the present invention to obviate or at least mitigate the foregoing disadvantages of the hydraulic locks of the downhole tools known in the art.

According to a first aspect of the present invention there is provided a hydraulic lock for locking the position of an actuation member of a downhole tool relative to the body of the downhole tool, the hydraulic lock comprising:

a first fluid chamber;

a second fluid chamber;

a first fluid conduit that provides a means for fluid communication between the first and second chambers;

a first logic controlled valve located within the first fluid conduit and moveable between an open configuration and a closed configuration to selectively permit fluid communication between the first and second chambers;

wherein the hydraulic lock further comprises a secondary control mechanism that provides

a second means to selectively permit fluid communication between the first and second chambers.

Incorporating a secondary control mechanism within the hydraulic lock provides a means for increasing the reliability and working lifetime of the hydraulic lock. It also provides a means for reducing the risk of unintentional or false activation of the hydraulic lock and thus any actuation member to which it is connected.

The first logic controlled valve preferably comprises a first valve controlled by a first valve control system. The valve may comprise a solenoid valve, an electro-mechanical valve or a hydraulic valve.

The first valve control system preferably comprises a first valve controller that provides a means for opening and closing the first valve. The first valve control system may further comprise one or more sensors configured to detect an activation event. Most preferably the first valve control system further comprises a first logic module that communicates with the one or more sensors and the first valve controller. When the one or more sensors detect an activation event, for instance a change in pressure, the first logic module checks the signal against a pre-programmed set of conditions, and if fulfilled, instructs the first valve controller to open or close the first valve depending on the nature of the signal.

Most preferably the first valve control system further comprises a battery pack to supply power to one or more of the one or more sensors, the first logic module and the first valve controller.

Optionally the one or more sensors comprise a first pressure sensor arranged to measure a pressure within the downhole tool and a second pressure sensor arranged to measure a pressure outside of the downhole tool. Alternatively, the one or more sensors comprise a motion sensor (e.g. accelerometers or gyroscopes) arranged to detect a motion within the downhole tool.

Optionally the secondary control mechanism comprises a second fluid conduit that provides a second means for fluid communication between the first and second chambers.

The secondary control mechanism may comprise a second logic controlled valve located within the second fluid conduit and moveable between an open configuration and a closed configuration to selectively permit fluid communication between the first and second chambers. In this embodiment the first and second logic control valves are effectively located in parallel between the first and second chambers and so the hydraulic lock unlocks if either the first or second logic controlled valves are moved to their open configurations.

The second logic controlled valve preferably comprises a second valve controlled by a second valve control system. The second valve may comprise a solenoid valve, an electro-mechanical valve or a hydraulic valve.

The second valve control system preferably comprises a second valve controller that provides a means for opening and closing the second valve. The second valve control system may further comprise one or more sensors configured to detect an activation event. Most preferably the second valve control system further comprises a second logic module that communicates with the one or more sensors and the second valve controller.

Most preferably the second valve control system further comprises a battery pack to supply power to one or more of the one or more sensors, the second logic module and the second valve controller.

Optionally the one or more sensors comprise a first pressure sensor arranged to measure a pressure within the downhole tool and a second pressure sensor arranged to measure a pressure outside of the downhole tool. Alternatively, the one or more sensors comprise a motion sensor (e.g. accelerometers or gyroscopes) arranged to detect a motion within the downhole tool.

Most preferably the one or more sensors of the second valve control system are of a different type to the one or more sensors of the first valve control system.

Alternatively, or additionally, the secondary control mechanism may comprise one or more pressure relief devices located within the second fluid conduit. Preferably the one or more pressure relief devices comprise one or more burst discs. Activation of the one or more pressure relief devices provides a secondary means of releasing the actuation member and thereby returning the downhole tool to its original configuration in the event of complete failure of the first logic controlled valve.

Optionally the secondary control mechanism comprises a third logic controlled valve located within the first fluid conduit. In this embodiment the first and third logic control valves are effectively located in series between the first and second fluid chambers and so the hydraulic lock only unlocks if both the first and third logic controlled valves are moved to their open configurations. This embodiment may be particularly appropriate where the downhole tool is required to function under an emergency situation, but where accidental activation of the actuation member could have serious undesirable consequences.

The third logic controlled valve preferably comprises a third valve controlled by a third valve control system. The third valve may comprise a solenoid valve, an electro-mechanical valve or a hydraulic valve.

The third valve control system preferably comprises a third valve controller that provides a means for opening and closing the third valve. The third valve control system may further comprise one or more sensors configured to detect an activation event. Most preferably the third valve control system further comprises a third logic module that communicates with the one or more sensors and the third valve controller.

Most preferably the third valve control system further comprises a battery pack to supply power to one or more of the one or more sensors, the third logic module and the third valve controller.

Optionally the one or more sensors comprise a first pressure sensor arranged to measure a pressure within the downhole tool and a second pressure sensor arranged to measure a pressure in the outside of the downhole tool. Alternatively, the one or more sensors comprise a motion sensor (e.g. accelerometers or gyroscopes) arranged to detect a motion within the downhole tool.

Most preferably the one or more sensors of the third valve control system are of a different type to the one or more sensors of the first valve control system.

Optionally the secondary control mechanism comprises a timer unit connected to the first logic controlled valve the timer unit providing a means for automatically unlocking the hydraulic lock. When the hydraulic lock is unlocked in this manner an operator is able to reset the actuation member of the downhole tool to its original position.

Preferably the timer unit automatically unlocks the hydraulic lock at predetermined periodic intervals.

Optionally the secondary control mechanism comprises a piercing tool having a bore and one or more piercing elements wherein the one or more piercing elements are located adjacent to the first and or second fluid chambers. Preferably the piercing tool comprises two piercing elements one of which is located adjacent to the first fluid chamber and the other is located adjacent to the second fluid chamber. Most preferably the one or more piercing elements are activated in response to a predetermined pressure within the bore.

According to a second aspect of the present invention there is provided a downhole tool comprising:

a body;

an actuation member moveable relative to the body;

an actuation arrangement configured to move the actuation member relative to the body;

and a hydraulic lock in accordance with the first aspect of the present invention,

wherein the hydraulic lock is configured in a first configuration to permit movement of the actuation member by the actuation arrangement and configured in a second configuration to provide a fluid lock across the actuation member which prevents movement of the actuation member by the actuation arrangement.

Embodiments of the second aspect of the invention may comprise features to implement the preferred or optional features of the first aspect of the invention or vice versa.

According to a third aspect of the present invention there is provided a method for increasing the reliability of a hydraulic lock comprising: a first fluid chamber; a second fluid chamber; a first fluid conduit that provides a means for fluid communication between the first and second chambers and a first logic controlled valve located within the first fluid conduit and moveable between an open configuration and a closed configuration to selectively permit fluid communication between the first and second chambers; the method comprising providing the hydraulic lock with a secondary control mechanism that provides a second means to selectively permit fluid communication between the first and second chambers.

Optionally providing the hydraulic lock with a secondary control mechanism comprises providing a second means for fluid communication between the first and second chambers.

Providing the hydraulic lock with a secondary control mechanism may further comprise providing a second logic controlled valve moveable between an open configuration and a closed configuration within the second fluid conduit.

Providing the hydraulic lock with a secondary control mechanism may further comprise providing one or more pressure relief devices within the second fluid conduit.

Providing the hydraulic lock with a secondary control mechanism may further comprise providing a third logic controlled valve moveable between an open configuration and a closed configuration within the first fluid conduit.

Providing the hydraulic lock with a secondary control mechanism may further comprise providing a means to automatically unlock the hydraulic lock. The hydraulic lock may be automatically unlocked at predetermined periodic intervals.

Providing the hydraulic lock with a secondary control mechanism may further comprise locating one or more piercing elements adjacent to the first and or second fluid chambers. Most preferably the method further comprises providing a predetermined pressure to activating the one or more piercing elements.

Embodiments of the third aspect of the invention may comprise features to implement the preferred or optional features of the first or second aspects of the invention or vice versa.

According to a fourth aspect of the present invention there is provided a downhole tool comprising a switchable hydraulic lock as the means of controlling actuation and a plurality of independent control mechanisms, any one of which can be independently operated to control the tool.

Preferably the downhole tool comprises two independent control mechanisms. According to a fifth aspect of the present invention there is provided a downhole tool comprising a switchable hydraulic lock as the means of controlling actuation and a plurality of independent control mechanisms, a plurality of which are required to be operated to control the tool.

Preferably the downhole tool comprises two independent control mechanisms

According to a sixth aspect of the present invention there is provided a downhole tool comprising a switchable hydraulic lock as the means of controlling actuation and a time-based automatic reset for unlocking the hydraulic lock.

According to a seventh aspect of the present invention there is provided a downhole tool comprising a switchable hydraulic lock as the means of controlling actuation and a pressure activated device for unlocking the hydraulic lock.

According to an eighth aspect of the present invention there is provided a downhole tool comprising a switchable hydraulic lock as the means of controlling actuation and a means of permanently disabling the hydraulic lock.

According to a ninth aspect of the present invention there is provided a downhole tool comprising a switchable hydraulic lock as the means of controlling actuation and a means of permanently disabling the hydraulic lock wherein the permanent disabling means comprises a further downhole tool able to rupture the walls of the hydraulic chambers of the hydraulic lock.

Embodiments of the fourth to ninth aspects of the invention may comprise features to implement the preferred or optional features of the first to third aspects of the invention or vice versa.

BRIEF DESCRIPTION OF DRAWINGS

There will now be described, by way of example only, various embodiments of the invention with reference to the drawings, of which:

FIG. 1 presents a longitudinal section view of a downhole tool incorporating a hydraulic lock as known in the art, shown in a retracted configuration;

FIG. 2 presents a longitudinal section view of the downhole tool of FIG. 1 shown in an extended configuration;

FIG. 3 presents a section view of the hydraulic lock of the downhole tool of FIG. 1;

FIG. 4(a) presents a section view of a hydraulic lock in accordance with an embodiment of the present invention while FIG. 4(b) presents a schematic view of a control system module for the hydraulic lock;

FIG. 5 presents a section view of a hydraulic lock in accordance with an alternative embodiment of the present invention;

FIG. 6 presents a section view of a hydraulic lock in accordance with an alternative embodiment of the present invention;

FIG. 7 presents a section view of a hydraulic lock in accordance with an alternative embodiment of the present invention;

FIG. 8 presents a section view of a hydraulic lock in accordance with an alternative embodiment of the present invention; and

In the description which follows, like parts are marked throughout the specification and drawings with the same reference numerals. The drawings are not necessarily to scale and the proportions of certain parts have been exaggerated to better illustrate details and features of embodiments of the invention.

DETAILED DESCRIPTION

FIG. 1 presents a longitudinal section view of a downhole tool 10 disclosed with within international patent application WO 2014/009756 in a retracted configuration while FIG. 2 present the downhole tool 10 in an extended configuration. The downhole tool 10 can be seen to comprise an actuation member in the form of a piston 1 positioned and moveable within a bore 16 of an annular body 2 and sealed therein with sealing elements 3 a, 3 b and 4. The downhole tool 10 further comprises an actuating piston 46 and, in use, the actuating piston 46 forms an actuation arrangement for the tool 10. In the illustrated embodiment, the actuating piston 46 includes a separate component coupled to an upper end of the annular body 2, although the actuating piston 46 could alternatively be formed by the body 2. As shown in FIGS. 1 and 2, the actuating piston 46 sealingly engages with the body 2 and has an upper end face 48 which is exposed to flow and pressure in the bore 16 and a lower end face 58 which is exposed to annulus flow and pressure via a port 52 in the body 2. In use, differential pressure acting across the larger area of the upper end face 48 of the actuating piston 46 urges the actuating piston 46 and the piston 1 towards the extended configuration as shown in FIG. 2.

The downhole tool 10 also comprises a hydraulic lock 20, further details of which are presented in FIG. 3. The hydraulic lock can be seen to comprise fluid chambers 5 a and 5 b that are filled with hydraulic fluid; a hydraulic line 6 a and 6 b that connects fluid chambers 5 a and 5 b; and a logic controlled valve 7, for example a solenoid valve, placed in the hydraulic line 6 a and 6 b. Hydraulic fluid chamber 5 a is sealed by seals 3 b and 4 while hydraulic fluid chamber 5 b is sealed by seals 3 a and 4. The hydraulic line 6 a runs from hydraulic fluid chamber 5 a to the solenoid valve 7 while the hydraulic line 6 b runs from the solenoid valve 7 to the hydraulic fluid chamber 5 b. When the solenoid valve 7 is closed hydraulic fluid cannot flow between fluid chambers 5 a and 5 b and the piston 1 cannot move within the annular body 2. When the valve 7 is open the piston 1 is able to move within the body 2, subject to an external load being applied. A control system 8 which may comprise a power supply, sensors and appropriate electronic circuitry provide logic control for the valve 7 i.e. control whether the valve 7 is open or closed. The power supply may be batteries and the sensors may be pressure transducers or accelerometers or gyroscopes for instance. When the sensors detect a signal, for instance a change in fluid pressure, the electronic circuitry checks the signal against a pre-programmed set of conditions, which if fulfilled, allows the valve 7 to open or close depending on the nature of the signal thus moving the downhole tool 10 between the retracted configuration of FIG. 1 and the extended configuration of FIG. 2.

FIG. 4(a) presents a section view of a hydraulic lock 40 in accordance with a first embodiment of the present invention. In the presently described embodiment, the hydraulic lock 40 comprises first 20 a and second locks 20 b connected in parallel between the hydraulic chambers 5 a and 5 b. As can be seen from FIG. 4(a) in this embodiment the arrangement of hydraulic lines 6 and control system 8 is effectively duplicated. There are two solenoid valves 7 a and 7 b and two control systems 8 a and 8 b. Solenoid valve 7 a is connected to the hydraulic chambers 5 a and 5 b by hydraulic lines 6 a and 6 b. Solenoid valve 7 b is connected to the hydraulic chambers 5 a and 5 b by hydraulic lines 6 c and 6 d.

Each control system 8 a and 8 b comprises a control system module 42 as presented in FIG. 4(b). The control system module 42 can be seen to comprise a first pressure transducer 44 a arranged to communicate with pressure in the bore 16 and a second pressure transducer 44 b arranged to communicate with pressure in the annulus. The control system module 42 further comprises a transducer logic module 45 that communicates with the first and second pressure transducers 44 a and 44 b and a solenoid valve controller 47. The solenoid valve controller 47 controls the respective valve 7 a or 7 b. A battery pack 49 is also provided to supply power to the transducer logic module 45 and the solenoid valve controller 47.

The control system module 42 may be configured to receive the activation event. The control system module 42 may additionally be configured to transmit information to and or receive information the surface.

In this embodiment the hydraulic lock 40 unlocks if either control system 8 a or 8 b operates its respective solenoid valve 7 a or 7 b. The primary control system 8 a and secondary control system 8 b may be identical as described above. It may be preferable for the secondary control system 8 b to comprise different types of sensors to that of the primary control system 8 a. For instance, if the primary control system 8 a comprises pressure transducers 44 a and 44 b, the secondary control system 8 b may comprise accelerometers.

It is of course a simple matter to contemplate adding a tertiary control system, which would provide even greater reliability. In a further alternative embodiment the hydraulic lock 40 may comprise more than two hydraulic locks connected in parallel between the hydraulic chambers 5 a and 5 b.

The second hydraulic lock 20 b of the above described hydraulic lock 40 provides a secondary control mechanism that acts as backup arrangement partially or completely independent of the primary lock 20 a. The primary control system 8 a may comprise pressure transducers programmed to look for a pre-determined sequence of pressure signals. Should this system fail, say through malfunction of the control system 8 a electronics, there is provided a backup system, a secondary lock 20 b, with an independent power supply, the control system 8 b of which may for instance comprise accelerometers programmed to look for a pre-determined sequence of rotational operations, say 100 rotations of the drill string followed by one minute with no rotations followed by a further 100 rotations. The advantage of hydraulic lock 40 is that it extends the mean time to failure of the actuator member 1 and thereby improves its reliability.

FIG. 5 presents a section view of a hydraulic lock 50 in accordance with a second embodiment of the present invention. In the presently described embodiment, the hydraulic lock 50 comprises first 20c and second locks 20d connected in series between the hydraulic chambers 5 a and 5 b. As can be seen from FIG. 5 there are two solenoid valves 7 c and 7 d and two control systems 8 c and 8 d. Solenoid valve 7 c is connected to the hydraulic chambers 5 a by hydraulic line 6 e. Solenoid valve 7 d is connected to the hydraulic chamber 5 b by hydraulic line 6 g. A hydraulic line 6f connects the two solenoid valves 7 c and 7 d. The first control system 8 c is employed to control solenoid valve 7 c, while the second control system 8 d is employed to control the other solenoid valve 7 d. In this embodiment, both control systems 8 c and 8 d are required to operate their respective solenoid valve 7 c and 7 d for the hydraulic lock 50 to be unlocked.

It is of course a simple matter to contemplate adding a tertiary control system, which would provide even greater reliability. In a further alternative embodiment the hydraulic lock 50 may comprise more than two hydraulic locks 20 connected in series between the hydraulic chambers 5 a and 5 b.

The second hydraulic lock 20 d of the above described hydraulic lock 50 again provides a secondary control mechanism that acts as backup arrangement partially or completely independent of the primary lock 20 c. However, in this embodiment the two systems 20 c and 20 d are arranged in sequence. For instance pre-programmed signals would be required to operate both control systems 8 c and 8 d before the hydraulic lock 50 would unlock (or lock) thus allowing the downhole tool 10 to move between the retracted configuration of FIG. 1 and the extended configuration of FIG. 2.

This embodiment may be particularly appropriate where the downhole tool 10 is required to function under an emergency situation, but where accidental functioning could have serious undesirable consequences. An example of such a scenario might be a downhole valve designed to obstruct flow in a well control situation. Accidental operation of such a valve could have serious consequences in terms cost and safety and so ‘dual key’ operation instructions would have significant benefits.

FIG. 6 presents a section view of a hydraulic lock 60 in accordance with a third embodiment of the present invention. In the presently described embodiment, the hydraulic lock 60 comprises a pre-programmed timer 9 connected to the control system 8 e. The function of the timer 9 is to instruct the control system 8 e to open the valve 7 e after a predetermined time has elapsed since the last valve opening instruction was sent. The period may for instance be two hours.

The pre-programmed timer 9 of the above described hydraulic lock 60 again provides a secondary control mechanism that acts as backup arrangement partially or completely independent of the primary lock 20 e. In this embodiment, the pre-programmed timer 9 may be programmed to automatically open the hydraulic lock 60 to allow the downhole tool 10 to be reset to its the original configuration at periodical intervals. An example of a situation where this might be desirable is in the case of an expandable underreamer whose arms are extended, and when it comes time to retract the arms it is found that the control system 8 e for the primary hydraulic lock 20 e has failed. In this situation, unless the underreamer arms are retracted, it can be extremely difficult to recover the drill string from the well. If for instance, the signal sensors (pressure transducers, accelerometers or the like) had failed, the automatic reset provided by the pre-programmed timer 9 would unlock hydraulic lock 60 and so allow the underreamer to return to its retracted position thus allowing it to be recovered from the well. If in the normal course of operations, the actuator piston 1 resets when and there has been no failure, it is simply a matter of the operator re-activating the actuator piston 1 to continue with the desired downhole operations.

FIG. 7 presents a section view of a hydraulic lock 70 in accordance with a fourth embodiment of the present invention. In the presently described embodiment, the hydraulic lock 70 comprises one or more pressure relief devices 110 in the form of one or more burst discs connected in parallel with a primary lock 20 f to hydraulic chambers 5 a and 5 b by hydraulic lines 6h and 6j. In this embodiment, if the control system 8 f or the solenoid valve 7 f were to fail to operate, a high pressure could be applied to the bore 16 of the downhole tool 10 which would then generate a high pressure in hydraulic chamber 5 a and hydraulic line 6 h thereby rupturing the one or more burst discs 110 and allowing hydraulic fluid to travel between hydraulic chambers 5 a and 5 b, thereby allowing the downhole tool 10 to reset.

The one or more burst discs 110 of the above described hydraulic lock 70 again provides a secondary control mechanism that acts as backup arrangement partially or completely independent of the primary lock 20 f. The burst discs 110 therefore provides a secondary means of releasing the actuator piston 1 and thereby returning the downhole tool 10 to its original configuration in the event of complete failure of the control system 8 f or the solenoid valve 7 f. An example of a situation where this might be desirable could again be the case of the underreamer described in the third embodiment above. As an example, a dart may be pumped down the bore 16 of the downhole tool 10 to land on a seat below the hydraulic lock 70 and pressure would be applied to burst the one or more burst discs 110 and thereby release the hydraulic lock 70. The burst discs 110 rupture pressure would be set at a pressure considerably above any pressure normally seen in the operation of the downhole tool 10 in order to avoid accidental rupturing.

FIG. 8 presents a section view of a hydraulic lock 80 in accordance with a fifth embodiment of the present invention. In the presently described embodiment, the hydraulic lock 80 comprises a piercing tool 12 having piercing elements 15 a and 15 b. The piecing tool 12 is run down the drill string (not shown) and located in the actuator piston 1 such that the piercing elements 15 a and 15 b are located adjacent to hydraulic chambers 5 a and 5 b, respectively. Applying high pressure to the bore 14 of the piercing tool 12 causes piercing elements 15 a and 15 b to extend and rupture the walls of the actuator piston 1 at points 17 a and 17 b. The ruptures allow fluid communication between hydraulic chambers 5 a and 5 b as both effectively evacuate into bore 16 of annular body 2, thereby allowing the downhole tool 10 to be reset.

The piecing tool 12 of the above described hydraulic lock 80 again provides a secondary control mechanism that acts as backup arrangement partially or completely independent of the primary lock 20 g. This specially designed tool is initially lowered into the actuator piston 1 and thereafter pressure is applied to cause the tool 12 to rupture the wall of the actuator piston 1 thereby releasing the hydraulic lock 80 and allowing the actuator piston 1 to retract to its non-actuated position e.g. by spring return.

In an alternative embodiment, the piecing tool 12 may comprise a single piercing element 15 a. This is a less preferable embodiment as it would require an operator to make a decision with regards which of the hydraulic chambers 5 a or 5 b the a single piercing element 15 a should be located adjacent to in order to release the hydraulic lock 80 and allow the actuator piston 1 to retract to its non-actuated position. In practice, a second single piercing element 15 a piecing tool 12 may be required in order to rupture and evacuate the other hydraulic chambers 5 a or 5 b.

In a further alternative embodiment the variation of the piecing tool 12 could be arranges to locate within a groove in the actuator piston 1. After rupturing the wall of the actuator piston 1, an upward pull would lift the actuator piston 1 to its non-actuated position without the need to rely on a spring return force.

The above described embodiments have been described with reference to a downhole tool comprising an actuation member in the form of a piston. It will be appreciated that the actuation member could be employed to perform a range of downhole operations. Any suitable means for engaging the associated downhole tool or device to be controlled may be utilised. The actuation member of the downhole tool could be configured for direct attachment to, or otherwise configured to directly engage, the actuation mechanism or systems of the tool or device to be controlled. By way of example, the actuation member of the downhole tool may be utilised with a biasing piston or the like to move a sliding sleeve or other type of valve system to allow drill string pressure to act on the actuation piston or operating components of the tool or device to be controlled. Alternatively, or additionally, the actuation member of the downhole tool may be used with a biasing piston or the like to release and or re- apply a mechanical sear or trigger mechanism to pull a supporting sleeve from a finger collet type locking system or the like.

Embodiments of the present invention may provide a downhole tool for selectively actuating or operating an associated downhole tool or device and which is simple, reliable, is capable of real time activation, is selectively isolated from normal pumping flow and pressure requirements, and which permits the passage of further downhole tools, devices or equipment through the tool and does not require additional elements such as balls, darts or RFID tags to be pumped from surface to operate.

Providing a selective fluid lock across the actuation member permits the actuation member to be locked or held in place at any required position or stage of operation and for any required time interval. Since the actuation member is incapable of movement while the fluid lock is in place, the tool can be isolated from pressures, such as normal pumping flow and other pressure events, or other forces in the bore which may otherwise act on the actuation member.

It will be appreciated that the hydraulic locks can be configured to retain the actuation member in the retracted configuration, the extended configuration or in one or more intermediate position between the retracted configuration and the extended configuration. In addition the hydraulic locks lock may be separate from and/or isolated from the actuation arrangement.

The described hydraulic locks may comprise a closed fluid system. It will be appreciated that the first fluid chamber 5 a and the second fluid chamber 5 b may be configured to receive a fluid which may include a hydraulic fluid, such as hydraulic oil or other suitable fluid. Providing a substantially incompressible fluid in a closed fluid system permits the fluid lock to be created across the actuation member in use.

The above described valve may be of any suitable alternative form and construction e.g. an electro-mechanical valve or a pilot valve.

The described downhole tool may form part of a downhole tool string. A connection arrangement may be provided for coupling the downhole tool to other components of the tool string. The connection arrangement may include threaded connectors, such as a threaded box and pin connectors

The present invention provides a remotely actuated downhole tool comprising a switchable hydraulic lock as the means of controlling actuation, wherein secondary means of control is also incorporated within the hydraulic lock in order to improve the reliability of the actuator or to allow it to perform operations requiring a ‘dual key’ system of control.

A hydraulic lock for locking the position of an actuation member of a downhole tool relative to the body of the downhole tool is described. The hydraulic lock comprises first and second fluid chambers, fluid communication between which is provided by a first fluid conduit. Located with the first fluid conduit is a first logic controlled valve that is moveable between an open configuration and a closed configuration to selectively permit fluid communication between the first and second chambers. The hydraulic lock further comprises a secondary control mechanism that provides a second means to selectively permit fluid communication between the first and second chambers. Incorporating the secondary control mechanism within the hydraulic lock provides a means for increasing the reliability and working lifetime of the hydraulic lock. It also provides a means for reducing the risk of unintentional or false activation of the hydraulic lock.

Throughout the specification, unless the context demands otherwise, the terms “comprise” or “include”, or variations such as “comprises” or “comprising”, “includes” or “including” will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers.

Furthermore, reference to any prior art in the description should not be taken as an indication that the prior art forms part of the common general knowledge.

The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The described embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilise the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, further modifications or improvements may be incorporated without departing from the scope of the invention as defined by the appended claims. 

1. A hydraulic lock for locking the position of an actuation member of a downhole tool relative to the body of the downhole tool, the hydraulic lock comprising: a first fluid chamber; a second fluid chamber; a first fluid conduit that provides a means for fluid communication between the first and second chambers; a first logic controlled valve located within the first fluid conduit and moveable between an open configuration and a closed configuration to selectively permit fluid communication between the first and second chambers; wherein the hydraulic lock further comprises a secondary control mechanism that provides a second means to selectively permit fluid communication between the first and second chambers.
 2. A hydraulic lock as claimed in claim 1 wherein the first logic controlled valve comprises a first valve controlled by a first valve control system.
 3. A hydraulic lock as claimed in claim 2 wherein the valve comprises a solenoid valve, an electro-mechanical valve or a hydraulic valve.
 4. A hydraulic lock as claimed in claim 2 wherein the first valve control system comprises a first valve controller that provides a means for opening and closing the first valve.
 5. A hydraulic lock as claimed in claim 4 wherein the first valve control system further comprises one or more sensors configured to detect an activation event.
 6. A hydraulic lock as claimed in claim 5 wherein the first valve control system further comprises a first logic module that communicates with the one or more sensors and the first valve controller.
 7. A hydraulic lock as claimed in claim 5 wherein the first valve control system further comprises a battery pack to supply power to one or more of the one or more sensors, the first logic module and the first valve controller.
 8. A hydraulic lock as claimed in claim 5 wherein the one or more sensors comprise a first pressure sensor arranged to measure a pressure within the downhole tool and a second pressure sensor arranged to measure a pressure outside of the downhole tool.
 9. A hydraulic lock as claimed in claim 5 wherein the one or more sensors comprise a motion sensor arranged to detect a motion within the downhole tool.
 10. A hydraulic lock as claimed in claim 1 wherein the secondary control mechanism comprises a second fluid conduit that provides a second means for fluid communication between the first and second chambers.
 11. A hydraulic lock as claimed in claim 10 wherein the secondary control mechanism comprises a second logic controlled valve located within the second fluid conduit and moveable between an open configuration and a closed configuration to selectively permit fluid communication between the first and second chambers.
 12. A hydraulic lock as claimed in claim 11 wherein the second logic controlled valve comprises a second valve controlled by a second valve control system.
 13. A hydraulic lock as claimed in claim 12 wherein the second valve control system comprises a second valve controller that provides a means for opening and closing the second valve.
 14. A hydraulic lock as claimed in claim 12 wherein the second valve control system further comprises one or more sensors configured to detect an activation event.
 15. A hydraulic lock as claimed in claim 14 wherein the second valve control system further comprises a second logic module that communicates with the one or more sensors and the second valve controller.
 16. A hydraulic lock as claimed in claim 14 wherein the second valve control system further comprises a battery pack to supply power to one or more of the one or more sensors, the second logic module and the second valve controller.
 17. A hydraulic lock as claimed in claim 14 wherein the one or more sensors comprise a first pressure sensor arranged to measure a pressure within the downhole tool and a second pressure sensor arranged to measure a pressure in the outside of the downhole tool.
 18. A hydraulic lock as claimed in claim 14 wherein the one or more sensors comprise a motion sensor arranged to detect a motion within the downhole tool.
 19. A hydraulic lock as claimed in claims 14 wherein the one or more sensors of the second valve control system are of a different type to the one or more sensors of the first valve control system.
 20. A hydraulic lock as claimed in claim 10 wherein the secondary control mechanism comprise one or more pressure relief devices located within the second fluid conduit.
 21. (canceled)
 22. A hydraulic lock as claimed in claim 1 wherein the secondary control mechanism comprises a third logic controlled valve located within the first fluid conduit.
 23. (canceled)
 24. (canceled)
 25. (canceled)
 26. (canceled)
 27. (canceled)
 28. (canceled)
 29. (canceled)
 30. (canceled)
 31. A hydraulic lock as claimed in claim 1 wherein the secondary control mechanism comprises a timer unit connected to the first logic controlled valve the timer unit providing a means for automatically unlocking the hydraulic lock.
 32. A hydraulic lock as claimed in claim 31 wherein the timer unit automatically unlocks the hydraulic lock at predetermined periodic intervals.
 33. (canceled)
 34. (canceled)
 35. (canceled)
 36. A downhole tool comprising: a body; an actuation member moveable relative to the body; an actuation arrangement configured to move the actuation member relative to the body; and a hydraulic lock as claimed in claim 1, wherein the hydraulic lock is configured in a first configuration to permit movement of the actuation member by the actuation arrangement and configured in a second configuration to provide a fluid lock across the actuation member which prevents movement of the actuation member by the actuation arrangement.
 37. A method for increasing the reliability of a hydraulic lock comprising: a first fluid chamber; a second fluid chamber; a first fluid conduit that provides a means for fluid communication between the first and second chambers and a first logic controlled valve located within the first fluid conduit and moveable between an open configuration and a closed configuration to selectively permit fluid communication between the first and second chambers, the method comprising providing the hydraulic lock with a secondary control mechanism that provides a second means to selectively permit fluid communication between the first and second chambers.
 38. A method for increasing the reliability of a hydraulic lock as claimed in claim 37 wherein providing the hydraulic lock with a secondary control mechanism comprises providing a second means for fluid communication between the first and second chambers.
 39. A method for increasing the reliability of a hydraulic lock as claimed in claims 38 wherein providing the hydraulic lock with a secondary control mechanism further comprises providing a second logic controlled valve moveable between an open configuration and a closed configuration within the second fluid conduit.
 40. A method for increasing the reliability of a hydraulic lock as claimed in claim 38 wherein providing the hydraulic lock with a secondary control mechanism further comprises providing one or more pressure relief devices within the second fluid conduit.
 41. A method for increasing the reliability of a hydraulic lock as claimed in claim 37 wherein providing the hydraulic lock with a secondary control mechanism further comprises providing a third logic controlled valve moveable between an open configuration and a closed configuration within the first fluid conduit.
 42. A method for increasing the reliability of a hydraulic lock as claimed claim 37 wherein providing the hydraulic lock with a secondary control mechanism further comprises providing a means to automatically unlock the hydraulic lock.
 43. A method for increasing the reliability of a hydraulic lock as claimed in claim 42 wherein the hydraulic lock is automatically unlocked at predetermined periodic intervals.
 44. (canceled)
 45. (canceled)
 46. (canceled)
 47. (canceled)
 48. (canceled)
 49. (canceled)
 50. (canceled) 